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K.O. Oxidized Oil Stains with KOH

Norm Oehlke |

Most yellow or yellow/brown stains that reach the spotter originate from a beverage, liquor or fruit-juice substance. However, some yellow stains won’t respond to wet-side spotting or the use of bleaches. In such cases, the stain is likely an oily stain, from any number of cooking oils or butter.
Oil stains are colorless on first contact with a garment, showing up only as “damp” areas. Age and heat cause them to oxidize and turn yellow. What appeared to be a stain-free garment at the time you accepted it at the counter often has yellow stains after cleaning. Oils can also oxidize and yellow in storage.
Customers seldom realize that an oily substance has stained a garment and hang it in the closet. This is when the invisible stain starts to yellow. The same yellowing occurs when beverages, mixed drinks and fruit juices stain a garment, however. So how will you know if it’s a dry-side oil stain or a wet-side beverage stain?
The following clues can help identify an oil stain, but they’re not always 100% accurate. The best way to identify an oil stain is to look for wicking around the outer edges. Oil follows the yarns in a weave, forming crosses. Wet-side stains don’t form crosses. Oil stains are also often yellow, but they could be black from the presence of dirt and dyes.
Oils have a strong affinity for synthetic fibers such as nylon, polyester and acetate. Therefore, a yellow stain on white polyester is usually an oil stain. If the stain is forming crosses, it’s an even stronger indicator. If the spotter notices a stain like this, there’s a 99.9% chance that it’s oil, and it can’t be removed with wet agents or bleach—it requires a dry-side agent.Stain Removal. Place the stained area on the solid portion of the board, wet it out with VDS and tamp well—brushing is usually ineffective. Short, rapid tamping with the bristles hitting squarely on the board is best. Keep the stain flooded with VDS while tamping. Occasionally flush off loosened oil, reapply more VDS and tamp.
The presence of carbon in the oil requires an application of POG with the VDS, followed by tamping. Be patient; it will take a few seconds for the oils to loosen. Once the stain is solubilized, flush the area well with VDS or reclean.
Surface pigments and dyes may solubilize with repeated applications of VDS and POG. If in doubt, check the pigments’ colorfastness on an unexposed area of the garment first.
Drycleaners often ask if there is another agent to use when typical dry-side agents fail. There is: A solution of butyl alcohol and potassium hydroxide, or KOH.
Once an oil stain has been left on a fabric for an extended time or exposed to heat, the usual spotting process will not be effective. However, KOH solution will do the job. I’ve used KOH my entire career and have been amazed how well it works.
Potassium hydroxide is a strong alkali when dissolved in water; in this form, it can damage silk and wool. But when potassium hydroxide is dissolved in butyl alcohol, it makes a solvent capable of removing the most oxidized oil stains—regardless of type, age or heat exposure.
The solution is not as strong with alcohol because no moisture is present. It’s prepared by dissolving 50 grains (1/4 tsp.) of potassium hydroxide in one quart of butyl alcohol. Once dissolved, it is ready to use.
Unfortunately, potassium hydroxide and butyl alcohol can only be purchased from chemical-supply houses. Butyl alcohol usually comes in one- or five-gallon quantities, and a quart of KOH solution will be enough for one drycleaner for six months to a year. Several cleaners may want to go in on a purchase to share the cost.
When using KOH, be sure all other spotting agents are removed from the stained area, and the area is dry. Apply KOH directly to the stain over a towel. Wait 10 to 15 minutes and flush with drycleaning solvent—not VDS. Reclean the item to be sure all agents are removed.
Never use moisture in combination with KOH. This will form a strong alkali capable of damaging fabrics. Wear gloves while using potassium hydroxide, and never touch the pellets with your fingers—it’s a strong alkali and will burn. Keep the KOH in a dark bottle in a cool, dark place and keep it tightly sealed. Don’t allow moisture or humidity to get into the bottle of potassium hydroxide, since it will no longer dissolve well in butyl alcohol.
When KOH contacts an oxidized oil stain, it usually intensifies its yellow color. Covering the stain once with KOH is often sufficient, but repeat applications are acceptable, if necessary. There is no value in tamping or brushing a stain wet with KOH—just allow it to remain there for 10 to 15 minutes, then reclean the garment.
KOH’s alkalinity will sometimes yellow a fabric, which will be noticeable after cleaning. To correct this, flush with steam, apply a few drops of tannin formula and flush again. Pigment prints may undergo similar color reactions that can be corrected with the application of an acid spotter. And never apply KOH to any type of foam-like backing such as urethane, acrylic or leather.
By using KOH in your plant, you’ll ensure greater customer satisfaction. The extra effort is to your advantage.

About the author

Norm Oehlke

Retired Columnist

Norm Oehlke was the author of American Drycleaner's Spotting Tips column from 1996 through 2007, as well as the author of American Drycleaner's Spotting Guide. Now retired, he spent a lifetime in the industry — first in a plant, and from 1955 through 1995 at IFI and its predecessor, NID. He resides with his wife, Adeline, in Highland, Md.

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